應用於無線通訊系統之電子式可調帶通濾波器

Abstract

在這篇論文中，我們發展了一個電子式可調帶通濾波器，這濾波器由開迴路環形共振器和varactor所構成。我們經由電路模擬來計算帶通濾波器的介入和反射損失，此外，我們也完成了實驗，且由模擬和量測相近的結果，我們更可確定電路模型的正確性。另外，在共振器上的varactor是用來調整共振器的共振頻率，如預期的，由varactor所造成的電抗確實的影響到共振器的總電感和電容值，值得一提的是，不僅濾波器的中心頻率可以被改變，這電抗是電感性或是電容性也將決定濾波器的中心頻率將大於或小於未加varactor時濾波器的中心頻率，利用這個結果，我們也實現了一個寬的可調頻率帶通濾波器，雖然不理想之二極體的Q值增加了濾波器的介入損失，但這原理是被證明可有效的用於調變帶通濾波器的中心頻率。

In this thesis, we developed an electrically tunable band-pass filter. The filter contains multiple sections of open-loop ring resonators and varactors. For the band-pass filter, the scattering parameters, including the insertion and return losses, has been calculated by means of electric circuit simulation. In addition, we have also carried out the experimental studies. The excellent agreements between simulated and measured results prove the accuracy of the established circuit model. Moreover, the varactor was added to the resonator to adjust its resonant frequency. As expected, the reactance introduced by the varactor indeed affects the net inductance and capacitance obviously. It is noted that, not only the shift with the center frequency, the inductive or capacitive of the reactance can also provide a parameter to switch its frequency toward the two directions away from the one without varactor. As a consequence, a wideband tunable band-pass filter is achieved. Although the bad quality factor with the diode strongly increases the insertion loss, this concept was proved to be available for effectively tuning the center frequency of such a class of band-pass filter.